In many applications it is desirable to avoid the use of metal pulleys, for example steel or aluminium, which may corrode and there is a great advantage in using polymeric materials for a pulley, the polymeric material not being liable to corrosion and being lighter in weight than say cast iron. However there are inherent difficulties due to the load strength of the polymeric material available, and the need for a large pulley to transmit high torque onto a relatively small shaft. Still further, polymeric material will creep as time passes, and its shape and size can both vary.
In the event that the polymeric material from which the pulley is made becomes loose on its shaft, it can suffer displacement in an axial direction. Accordingly, it is desirable to anchor a pulley to a shaft, and clearly desirable also that a bearing associated with the shaft should also be constrained against axial displacement.